Magnetic compass stabilizer



March 1, 1949. CHANCE 2,463,245

MAGNETIC COMPAS S STABILI ZER Original Filed Jan. 10, 1940 2 Sheets-Sheet 1 March 1, 1949. B, CHAQ E 2,463,245

MAGNETIC COMPASS STABILIZER' Original Fil ed Jan. 10, 1940 2 Sheets-Sheet 2 Patented Mar. 1, 1949 UNITED STATES PATENT OFFICE Original application January 10, 1940, Serial No. 313,283. Divided and this application October 13, 1944, Serial No. 558,521

8 Claims.

This invention relates to stabilization of a magnetic compass employed on a dirigible craft which is subject to rolling mot-ion tending to influence the compass adversely. More particularly, the invention relates to a novel stabilizing system which is responsive to movement of the compass card due to the crafts roll, and which functions to set up a corrective force counteracting such movement. The present application is a division of my prior application, Serial No. 313,283, filed January 10, 1940, from which issued Patent No. 2,360,330, October 17, 1944.

The invention is particularly applicable to the stabilization of a magnetic compass which forms part of an automatic steering system, and it will be described with particular reference to such a system, although it is to be understood that the invention is applicable generally to the stabilization of a magnetic compass which is subject to rolling motion of a dirigible craft.

The principal object of the invention, therefore, is to provide a novel stabilizing system for a magnetic compass, which is adapted to counteract movement of the compass card due to rolling motion of a dirigible craft on which the compass is employed.

A more specific object of the invention is to provide such a stabilizing system in conjunction with an automatic steering system so as to prevent false operation of the steering system in response to movement of the compass card due to rolling of the craft being steered.

The invention may be fully understood from the following detailed description with reference to the accompanying drawings illustrating a specific embodiment and in which:

Figs. 1 and 2 are explanatory illustrations by means of which the underlying principle of the invention may be clearly understood;

Fig. 3 is a sectional view of a compass binnacle embodying certain elements employed according to the invention;

' Fig. 4 is a plan view of the binnacle with the cover removed; and

Fig. 5 is a diagrammatic illustration of the complete apparatus in which the invention is embodied.

Before discussing the invention in detail, a clear understanding of the purpose and principle of operation of the invention may be had by ref erence to Figs. 1 and 2. In Fig. 1, there is represented at l a dirigible craft which, while shown in the general form of a ship or boat, is intended to be representative of dirigible crafts generally, including aircraft. A magnetic compass card is represented at 2, and the arrow 3 is intended to represent the magnet structure associated with the card 2. As will be understood, the compass card 2 normally remains directionally fixed under the influence of the earths magnetic field, and the craft l moves with respect to the card. At 4, there is represented a support mounted on the craft and carrying light-sensitive cells, such as photo-tubes 5 and 6. A light beam, whose direction is normally fixed, is represented by the broken line 1 extending outwardly from the compass between the cells 5 and 6. As will be seen later, the light beam remains directionally fixed as long as the compass card maintains its normal position. Whenever the craft 1 deviates from its course, one or the other of the light-sensitive cells 5 and 6 is brought into the path of the light beam, thus activating such cell. The selective activation of the light-sensitive cells may be utilized to control an automatic steering apparatus, as is well known in the prior art.

It is a known fact that a magnetic compass is adversely affected by rolling motion of a craft on certain headings, due to inherent dynamical unbalance and frictional forces within the compass structure. As may be seen in Fig, 1, transient rotation of the compass card 2, due to rolling motion of craft I, may cause the light beam 1 to impinge on one or the other of the light-sensitive cells 5 and 6, depending on the direction of the crafts roll, thereby producing undesired activation of one of the cells. The purpose of the present invention is to minimize the undesirable effects thus produced. In accordance with the invention, there are mounted on the support 4 a pair of electrical coils B and 9, which are normally deenergized and which are selectively energized in response to rolling motion of the craft in either direction and also in response to activation of the cells 5 and 6 due to such rolling motion. The manner in which the coils 8 and 9 are selectively energized will be fully described hereinafter.

The coils 8 and 9 are arranged in relation to the magnet structure of the compass so as to produce the desired corrective action. The manner in which this may be accomplished may be seen by reference to Fig. 2 in which the magnet structure of the compass is represented by the bar magnet l0 and the center of rotation of such structure is indicated at H. The coils 8 and 9 are arranged as illustrated to produce a rotative force on the compass magnet [0 whenever one of the coils is energized. Moreover, the direction of the current applied to each of the coils is such 3 as to properly polarize the magnetic field produced by the coil to counteract rotation of the compass magnet due to roll of the craft. Assume for example that the craft rolls in a direction to cause rotary movement of magnet Hi about its pivot H toward the left or counter-clockwise, as viewed in Fig. 2. In accordance with the present invention, the coil 8 is energized at that time by a current of the proper direction to produce a north magnetic pole at the right-hand end of the coil, which repels the north pole of the magnet l and quickly restores the magnet to its normal position. When the craft rolls in the opposite direction, causing rotationlof the magnet ii] to the right or clockwise, the coil 9 is energized in a manner to produce a north magnetic pole at its left-hand end, thus quickly restoring the magnet It to its normal position. Thus the invention operates to produce a corrective magnetic field in proper relation to the compass magnetwhenever the. craft rolls in one direction or the other.

Referring now to Figs. 3 and 4, there is illustrated a binnacle structure of the type shown in my prior Patent No. 2,185,074, granted December 26, 1939. This structure comprises a support or housing I2 whichis adapted to be readily mounted upon the craft at a predetermined position. A removable cover [3 serves, together with the support or housing, to house the elements of the device. Withinthe. housing thus provided there is mounted. a gimbal ring [4. which is attached to the support [2 by means of the opposed pin bearings or journals I 5 (see Fig. 4). As shown more clearly in Fig. 3', the gimbalring, M carries asuspended member IS in the form of an inverted hollow cone, which is supported by'means of diametrically opposed pin hearings or journals H. The member 16 is weighted as shown at I8 to maintain it in position and to resist movement due to rolling or other motionof the craft. A cup-shaped member [9 is rotatably supported by'member l6, and to. this end the member I9 is. provided with a centrally-disposed downwardly extending stud or spindle 20 which is rotatably supported on member 16' by means of the bearing structure 2i. A slip-ring structure 22- is arranged cooperatively with. the spindle 29 and servesto make electrical connection to the electrical elements carried by member H), as men'- tioned hereinafter. The side wall of the cupshaped member l'9' is supported by the rollers 23. which are carried upon adjustable brackets 24 secured to member It. The wall of member [9.- carries' a'worm-wheel 25 which meshes with a worm 2'6 rotatably carriedby an adjustable bracket 21 which is supported by member E6. The

viously mentioned, the selective activation of the light-sensitive cells in response to deviation of the craft from its course may be utilized to effect worm 26 is driven by a flexible shaft 28, thepurpose of which will be'expl'ained later.

The light-sensitive devices or photoelectric cells 5" and 6, hereinbefore mentioned, aremounted on the cup-shaped member l9 as shown. A spider29 isalsoc'arried by the cup-shapedmember l9 and serves to support the bowl 30 of the magnetic compass. A bracket 3|, also carried by the cupshaped member. l9, serves to support. a lamp. housing 32 in such manner that the lamp within the housing projectsa light beam downward substantially in axial alignment with theaxis of'the compass card 2. A reflecting device or mirror 33 is carried by the compass card. and is mounted in. substantial'alignment with the axis thereof, and this light-reflecting'device is adapted to reflect the light beam as shown'in Fig. 3. This arrangement provides a reflected beam of light whichis automatic steering, of which more will be said later.

In accordance with the present invention, the electrical coils 8. and 9, hereinbefore mentioned, are mounted on the cup-shaped member or cell carriage 19 (see Fig. 4) in proper relation to the compass magnet to giant the corrective action previously discussed. Infur-ther accordance with the invention; there is attached to the lowerportionof-thebinnacle structure a yoke 34; (see Fig. 5), which carries abar magnet35on which two. pickup coils 3B and 31 are freely disposedand are carried by a support 38 mounted on support [2. The magnet 35 and the associated-coils: and 3"| constitute an electromagnetic pick-up device which "generates electrical impulses in response to rolling motion of the craft, and. these impulses are supplied. in amplified form tothe coils B and. 9'. The said impulses are generated by relative movement betweenthe magnet '35 and the associated coils 3'6 and. 3.1, and since the yoke 34 remains substantially. stationary (by virtue of the gimbal mounting) while the coil-supporting bracket 38 rolls slightly when the craft rolls, there must besufiicient freedom of motion between the magnet and the coils to permit the necessary movement therebetween. To this end, the open.- ings through the coils, through-which the magnet 35 extends. are sufiiciently large to permit the necessary relative movement.

In order'that the coils 36 and 31 shall move relativeto the magnet 35- in response torolling motion or the craft about its axis of roll, i.-e.its longitudinal axis, it is necessary that the electromagnetic pick-up device be. properly orientated with respect to said axis. To this. end, the magnet 35 and the axis of coils 36' and 31. should be disposed in'transverse relation to the craftsaxis of roll. The pick-up device may be located in the immediate vicinity of the crafts axis of roll or it may be located'remot'e from said axis. Of course, if the pick-up device is supported by the com ass bi'n'nacl'e, as shown, the location of said device will be governed by th'e. location of the binnacle, but'th'e'pi'ck-up device may be separate from the compass binnacle, provided the said. device has one of its parts gimbaled and. the other part mounted for movement in response to rolling motion of the craft. It is immaterial, of. course; whether the cOiIsmOVe-reIatiVe to the magnet-or vice versa.

Referring now to Fig. 5,.there is illustrated-the complete apparatus or system embodying the structure 'h'ereinbefore described. In thisillustration the binnacle structureis. show-n diagrammatically. The'light-sensitive cells5 and 6 are connected to conventional vacuum-tube amplifiers 39 V and '40,. which, in turn, serve to actuate'a doubleacting relay 4] which controls the energ'iz'ati'on of a reversible motor 42. The motor may serve asta. steering motorand may have its armature. connected to -the steering rudder of the craft. The motor also drives the flexible shaft 28 to effect follow-up action through the worm 26 and the worm-wheel 25. The follow up action, as will be well understood, serves to restore the system to its normal equilibrium position. Thus, when the cell carriage moves in response to deviation of the craft from its course, causing operation of the motor 42, the follow up drive serves to move the cell carriage in the opposite direction to restore equilibrium.

The coils 36 and 31 are connected to the inputs of electronic amplifiers 43 and 44, each of which is normally inoperative but is rendered operative in response to operation of one of the amplifiers 39 and 40. As a simple illustration of the form which each of the amplifiers 43 and 44 may take, there is shown in each instance a screen grid tube 45 which is normally biased to cut-ofi by a negative potential applied to its screen grid, for example, by means of a biasing voltage source 46. The screen grid circuit in each instance is connected to the output of one of the amplifiers 3940 and this circuit includes a resistor 41, across which a voltage is produced in response to operation of the associated amplifier. The arrangement is such that the voltage across resistor 47 is of the proper polarity and of sufiicient magnitude to overcome the negative bias on the screen grid of tube 45 and thus render the tube operative. Thus, each time one of the light-sensitive cells 5 and 6 is activated, one or the other of the amplifiers 43 and 44 is rendered operative, but no efiect is produced thereby unless a pulse is produced by the associated coil 36 or 31 in response to rolling of the craft, as will be more clearly seen later.

While the amplifiers 43 and 44 have been shown in simplified form, they may comprise as many stages as may be necessary to produce sufiicient amplification of the pulses from coils 36 and 31. Of course, only one stage need be biased in the manner illustrated. The outputs of amplifiers 43 and 44 are connected respectively to the correcting coils 3 and 9 which are mounted on the cell carriage 19.

Considering the operation of the system, as long as the craft does not roll there will be no relative motion between the magnet 35 and the coils 36 and 3? and therefore no impulse will be applied to the correcting coils 8 and 9, even though the amplifiers 43 and 44 are rendered operative selectively in response to operation of the automatic steering system. Accordingly, the automatic steering system functions in response to deviations of the craft from its course without any efiect upon the correcting coils 8 and 9.

If the craft rolls and causes rotation of the compass card 2 sufficiently to move the light beam onto one or the other of the light-sensitive cells 5 and 6, the corresponding amplifier 43 or 44 is rendered operative. At the same time, the rolling motion of the craft produces relative movement between magnet 35 and the coils 36 and 31. This movement generates voltages which are proportional to the velocity of the crafts roll. As a result, the amplifiers 43 and 44 receive impulses, and the amplifier which has been rendered operative supplies an amplified current impulse to the associated correcting coil 8 or 9. Thus, if the crafts roll causes counterclockwise rotation of the compass card 2, as viewed in Fig. 5, the light beam will activate cell 6 thereby rendering amplifier 43 operative. As a result, the impulse received from coil 36 will be amplified and applied to the coil 8, thus restoring the compass oard to its original position, as above described with reference to Fig. 2. Rotation of the compass card 2 in the opposite direction will cause activation of cell 5, thus rendering amplifier 44 operative and applying an impulse from coil 31 to the corrective coil 9. In either case, as soon as the light beam leaves the activated cell the controlled amplifier 43 or 44 is rendered inoperative and the energized coil 8 or 9 is deenergized.

The employment of the invention in conjunction with an automatic steering system, as illustrated in Fig. 5, effectively prevents operation of the steering system in response to rolling of the craft, since the correcting system quickly restores the equilibrium or neutral condition of the apparatus before the steering system has had time to operate appreciably. Since the steering system is relatively slow acting and is intended to operate in response to the low frequency yawing motion of the craft, the correcting action takes place before the steering system is enabled to respond to the undesired movement of the compass card.

The invention, substantially as illustrated and described, was applied experimentally to a craft of substantial size and its effectiveness to stabilize a magnetic compass was thus demonstrated.

While the invention has been described with reference to a specific embodiment, it will be understood that other embodiments may be resorted to, and various modifications may be made within the scope of the appended claims.

I claim:

1. Apparatus for stabilizing a magnetic compass on a dirigible craft which is subject to rolling motion, comprising angular displacementresponsive means for producing signals corresponding to the different senses of angular displacement of the compass magnet relative to the craft, a first normally inactive means adapted when activated to produce a magnetic force opposing the angular displacement of the compass magnet in one sense, a second normally inactive means adapted when activated to produce a magnetic force opposing the angular displacement of the compass magnet in the opposite sense, and means responsive to rolling motion of the craft and controlled by said signals to selectively activate the one of said last two means which is adapted to oppose the angular displacement of the compass magnet that caused the controlling signal, subject to correspondence in sense between the deflecting tendency of the rolling motion and the angular displacement of the compass magnet.

2. Apparatus for stabilizing a magnetic compass on a dirigible craft which is subject to rolling motion, comprising angular displacementresponsive means for producing signals corresponding to the different senses of angular displacement of the compass magnet relative to the craft, a first electrical means adapted when energized to produce a magnetic force opposing the angular displacement of the compass magnet in one sense, a second electrical means adapted when energized to produce a magnetic force opposing the angular displacement of the compass magnet in the opposite sense, and means responsive to rolling motion of the craft and controlled by said signals to selectively energize the one of said two electrical means which is adapted to oppose the angular displacement of the compass magnet that caused the controlling signal, subject to correspondence in sense between the deflecting cacao-45 7 tendency ofthe' rolling motion and the angular displacement of the'compass magnet.

3. Apparatus for stabilizing a magnetic compass ona dirigible craft which is subject to rolling motion, comprising angular displacementresponsive means for producing signals corresponding to the different senses of angular displacement of the compass magnet relative to the craft;.a. first electrical coil adapted-when energized to produce a magnetic force opposing the angular displacement of the compass magnet in one sense, a second electrical coil adapted when energized to produce a magnetic force opposing the angular displacement of the compass magnet in the opposite sense, electromagnetic pick-up means responsive to rolling motion of the craft for generating electrical impulses, and means controlled by said signals for transferring said impulses selectively to'the one of said coils which is adapted to oppose the angular displacement of the compass magnet that caused the controlling-signal, subject to correspondence in sense between the deflecting tendency of the rolling motion and the angular displacement of the compass magnet.

4. Apparatus for stabilizing a magnetic compass on a dirigible craft which is subject to rolling motion, comprising electro-optical means arranged to respond to angular displacement of the compass magnet relative to the craft, said electro-optical means including a pair of lightsensitive devices which are selectively activated in response to angular displacement of the compass magnet in different senses, thereby to produce signals corresponding to the different senses of said displacement, a first electrical means adapted when energized to produce a magnetic force opposing the angular displacement of the compass magnet in one sense, a second electrical means adapted when energized to produce a magnetic force opposing the angular displacementof the compass magnet in the opposite sense, and means responsive to rolling motion of the craft and controlled by said signals to selectively activate the one of said last two means which is adapted tooppose the angular displacement of the compass magnet that caused the controlling signal, subject to correspondence. in sense between the deflecting tendency of the rolling motion and the angular displacement of the compass magnet.

5. Apparatus for stabilizing a. magnetic compasson a'dirigible craft which is subject to rolling motion, comprising electro-optical means arranged to respond to angular displacement of the compass magnet relative to the craft, said electro-optical means including a pair of lightsensitive devices which are selectively activated in response to angular displacement of the. compass magnet in different senses, thereby to produce signals corresponding to the different senses of said displacement, a first. electrical means adapted when energized to produce a magnetic force opposing the angular displacement of: the compass magnet in one sense, asecond electrical means adapted when energized to produce a magnetic force opposing the angular displacement of the compass magnet in the opposite sense, means responsive to rolling motion of the craft for generating electrical impulses, and means controlled by said signals for transferring said impulses selectively to the one of said two electrical means which is adapted tooppose the angular displacement of the compass magnet that caused the'controlling signal, subject to corre- 8 spondence in sense between the deflecting tendency of the rolling-motion and the angular displacement of 'the compass magnet.

6; Apparatus for stabilizing a magnetic compass on a dirigible craft whichis subject to'rolling motion, comprising electro-optical means arranged to respond to angular displacement of the compass magnet relative to the craft, said electroopticalmeans including a pair of light sensitive devices which-are selectively activated'in response to angular displacement of the compass magnet in different senses, thereby to produce signals corresponding to the difierentsenses of said displacement, a pair of amplifiers connectedrespectively to said devices to amplify said'signals, a first electrical means adapted when ener gized to produce a magnetic force opposing the angular displacement of the compass magnet in one sense, asecond electrical means adapted when energized to produce a magnetic force opposing the angu1ar-displacement of the compass magnet in the opposite sense, means'responsive to rolling motion of the craft for generating electrical impulses said lastnamedmcans including a pair of coils, a pair of normally inoperativeamplifiers connected respectively to said coils, means controlled by the firstmentioned amplifiers forselectively rendering the last-mentioned amplifiers operative according to which of. said light-sensitive devices is activated, and meansconnecting saidlast-mentioned amplifiers to said first and second electrical means respectively-so as to selectively energize the latter to oppose the angular displacement of. the compass magnet, subjectto correspondence in sense between the deflectingat'endency of. the rolling motion and the angular displacementof the compass magnet.

7. Apparatusfor stabilizing a magnetic compass on a dirigible craft subject to rolling motion, comprising a binnaclestructure including a magnetic compass which is subject to. adverse influence by such motion, angular displacement-responsive means on said binnacle for producing. signals corresponding to the difierent sensesv of angular displacement of the compass magnet relativejto the craft, a first electrical coil on said binnacle adapted when energized to produce a magnetic force opposing the angular displacement of the compass magnet in one sense, a-secondelectrical coil on said binnacle adapted when energized to produce a magnetic force opposing the angular displacement of the compass magnet in the opposite sense, means responsive to the rolling motion of the craft for generating electrical impulses, and means controlled by said signals for transferring said impulses selectively to the one of said coils which is adaptedto oppose the angular displacement of the compass magnet that caused the controlling signal, subject to correspondence in sense between the deflecting tendency'of the rolling motion and the angular displacement of the compass magnet.

8. Apparatus for stabilizing a magnetic compass ona dirigible craft subject'to rolling motion, comprising a binnacle structure including a mag netic compass which is subject to'adverse' influence by such motion, angular displacement-responsive means on said binnacle for producing signals corresponding-to the different senses of angular displacement of the" compass magnet relative to the craft, a first electrical coil on said binnacle adapted when energized to produce a' magnetic force opposing the angular displacementof thecompassmagnetih one sense, a sec- 0nd electrical coil on said binnacle adapted when energized to produce a magnetic force opposing REFERENCES CITED the angular displacement of the compass magnet The following references are of record in the in the opposite sense, electromagnetic pick-up file Of this p te t means on said binnacle responsive to the rolling .5 UNITED STATES PATENTS motion of the craft for generating electrical impulses, and means controlled by said signals for Number Name ate transferring said impulses selectively to the one 1,535,210 ROIIX May 18, 1926 of said coils which is adapted to oppose the angu- 1,539,673 Winter June 22, 1926 lar displacement of the compass magnet that 1 2,135,074 a c Dec. 26, 1939 caused the controlling signal, subject to corre- 2,360,330 Chance 0t- 1944 spondence in sense between the deflecting tend- FOREIGN PATENTS ency of the rolling motion and the angular displacement of the compass magnet. Number Country Date BRIT-TON CHANCE 666,594 Germany Oct. 24, 1938 

